A coupling can be used with a hydraulic or pneumatic assembly to allow the selective connection of hydraulic or pneumatic lines. For example, a coupling can be used in a hook-up arrangement on an agricultural or industrial vehicle to operate an implement attached to or being towed by the vehicle. To this end, a coupling can comprise a housing and a pair of female couplers positioned within respective bores of the housing so that, when male couplers are coupled thereto, a flow path will be established between the male couplers and the supply/return lines of the assembly.
A female coupler can be movable between an operating position and a release position. In the operating position, a male coupler coupled to the female coupler will communicate with the supply/return line of the hydraulic or pneumatic assembly. In the release position, a male coupler can be released or “uncoupled” from the female coupler.
Lever-actuated cam members are commonly used to move the female coupler(s) from the operating position to the release position. In a coupling having a pair of female couplers, a lever moves the cam members to cause corresponding movement of the female couplers. In one known lever design, movement (i.e., rotation) of the lever's shaft results in parallel movement of the cam members and simultaneous interaction with the female couplers. In another known lever design, movement (i.e., pivoting) of the lever's shaft results in a see-saw movement of the cam members and independent interaction with the female couplers.
When uncoupling a male coupler from a female coupler, it is desirable to release pressure build-up within the female coupler prior to removal of the male coupler. This has been accomplished by the coupling incorporating (for each female coupler) a pressure relief valve movable from a closed position to an open position to prevent/permit the release of pressure from a flow passage inside the female coupler. With both the rotational lever design and the see-saw lever design, this can be accomplished by the cam member pushing the plunger of the pressure relief valve to the open position when the female coupler is moving towards the release position.
It is also often desirable to release pressure build-up within the female coupler prior to and/or during coupling of the male coupler thereto. With the rotational lever design, this has been accomplished by placing the female coupler in a coupling position whereat the cam member is abutted against a stop member thereby positioning the cam member to push the plunger and open the pressure relief valve. However, with the see-saw lever design, this arrangement is not possible, as such positioning of the cam member (if even possible) would result in the other cam member interacting with and moving its female coupler.